1. Field of the Invention
The present invention is related to an electric vehicle supply equipment control method, and more particularly, to a method that prevents fail-to-danger scenario of the electric vehicle supply equipment.
2. Description of the Prior Art
FIG. 1 is diagram illustrating a prior art electric vehicle supply equipment 100. The electric vehicle supply equipment 100 may include a switch 102, a relay 104, a relay controller 106, a controller 108, a current detector 110, and a communication unit 112. The relay 104 is used to control turning the switch 102 on and off. An input end of the switch 102 is coupled to an AC power source 122 and an output end of the switch 102 is coupled to a connector 120 for connecting to an electric vehicle. The AC power source 122 may be 110 VAC, 220 VAC, or other commonly used utility AC power source voltages. The electric vehicle supply equipment 100 may communicate with the electric vehicle via the communication unit 112 so that the communication unit 112 may verify that the connector 120 has been connected to the electric vehicle and the electric vehicle is ready to be charged by utilizing a control pilot signal CP and a proximity pilot signal PP of the electric vehicle supply equipment communication protocol. Next, the communication unit 112 may inform the controller 108 to output a control signal for controlling the relay controller 106 to turn on the relay 104 in order to turn on the switch 102 by the relay 104. After the switch 102 has been turned on, the AC power source 122 may be outputted to the connector 120 of the switch 102, which is connected to the electric vehicle, and begins to charge the electric vehicle.
The current detector 110 is utilized as a protection mechanism of the electric vehicle supply equipment 100. If a current outputted to the electric vehicle is higher than a predetermined value, the controller 108 controls the relay controller 106 for cutting off the switch 102 to avoid danger. However, if at least one of power components such as the switch 102, the relay 104, or the relay controller 106 of the electric vehicle supply equipment 100 fails, such as an abnormal short circuit happens, the aforementioned protection mechanism may not provide proper protection to prevent danger from happening. For example, if the switch 102 is short circuited, the AC power source 122 may deliver power to the connector 120 before the connection condition between the connector 120 and the electric vehicle and the electric vehicle's charge condition are confirmed by the communication unit 112, resulting in a fail-to-danger scenario.
Therefore, the switch 102, the relay 104, and other power components of the electric vehicle supply equipment 100 must be selected from components having safety levels higher than specific levels of SIL safety approval such as SIL2 or SIL3. Due to the fact that components meeting these levels of approval are expensive and difficult to purchase, it is the scope of the present invention to improve the protection mechanism of the electric vehicle supply equipment so as to meet the specific levels of SIL safety approval by using components with lower cost which are also easy to purchase.